How we calculate
Every gram figure on this site is grams per one US legal cup of 240millilitres. Volume units convert through each ingredient’s own density, mass units convert directly by weight, and where published references disagree we print both and say which one we follow. This page is the whole method, with nothing rounded off.
The base cup
A cup is not one thing. This site standardises on the US legal cup of exactly 240 millilitres, the definition the US Food and Drug Administration fixed for nutrition labelling in 21 CFR 101.9(b)(5)(viii), alongside a 5 ml teaspoon and a 15 ml tablespoon. It is also the round figure that most American recipe writing assumes, which matters more in practice than the legal status: if you found a recipe online, it was probably written against this cup.
The alternatives are real and the gaps between them are not trivial. The six standards we track, and what each one holds:
| Standard | Volume | Against the US legal cup | Where |
|---|---|---|---|
| US legal cup | 240 ml | reference | United States, nutrition labels and most modern recipe writing |
| US customary cup | 236.6 ml | -1.4% | United States, the strict legacy definition |
| Metric cup | 250 ml | +4.2% | Australia, New Zealand, and much of continental Europe |
| Imperial cup | 284.1 ml | +18.4% | United Kingdom, historical recipes |
| Canadian cup | 227.3 ml | -5.3% | Canada, pre-metrication recipes |
| Japanese cup | 200 ml | -16.7% | Japan, modern cooking |
The full explanation of each, including why the Australian tablespoon is the thing that actually catches people out, is on cup sizes by country.
From volume to weight
A cup measures volume and a gram measures mass, so the bridge between them is density. We store one figure per ingredient, its grams per US cup, and derive everything else from it:
- Millilitres: 1 cup = 240ml, and grams = millilitres multiplied by the ingredient’s grams per millilitre.
- Tablespoons: 1 tbsp = 15 ml, so 1 cup = 16 tablespoons exactly.
- Teaspoons: 1 tsp = 5 ml, so 1 cup = 48 teaspoons and 1 tablespoon = 3 teaspoons.
- Ounces: always ounces of weight, 1 oz = 28.3495 g. Never fluid ounces. See ounces versus fluid ounces.
- Pounds: 1 lb = 453.592 g = 16 ounces of weight.
Because everything derives from a single density, the numbers on the site can never disagree with each other by construction. Change one density and every table, every tablespoon figure and every sentence of prose that quotes it moves with it, because none of them are typed in by hand.
The spread this produces is wider than most people expect. A cup of panko breadcrumbs weighs about 50 grams and a cup of honey about 340 grams, a factor of 6.8 at exactly the same volume. That is the entire reason this site asks which ingredient you mean before it answers.
How figures are rounded
One function formats every number on the site, so the same quantity is never printed two different ways on two different pages. The rule is by significance rather than by unit:
| Value | Decimals | Example |
|---|---|---|
| Below 1 | 3 | 0.441 cups |
| 1 to 10 | 2 | 5.33 tbsp |
| 10 to 100 | 1 | 62.5 g |
| 100 and above | 0 | 227 g |
Trailing zeros are trimmed, so a value of 85.0 prints as 85. Prose may quote a friendlier rounded figure, but only ever with the word “about” attached; tables are always exact to the rule above.
What we do when sources disagree
They disagree constantly, and pretending otherwise would be the easiest way to lose your trust. The clearest example is the one at the centre of this site: King Arthur Baking publishes 120 grams for a cup of all-purpose flour, and this site prints 125. Neither is wrong. King Arthur assumes flour spooned into the cup and levelled off, which is the more careful method and gives a lighter cup; 125 grams is the figure the bulk of American recipe writing assumes. A four percent gap sounds like a lot until you measure the same cup twice yourself.
Our policy, in order:
- Record what each reference actually publishes, verbatim, next to our own figure. Never quietly adopt a source’s number and never round a source’s number to make it agree with ours.
- Say in plain words why we print the figure we print, on the ingredient page itself, under Where this figure comes from.
- Where we have not found a published reference, say exactly that, rather than gesturing at “reputable baking references” and letting it read like a citation.
- Never change a density without a source and a dated entry in the changelog.
Where we currently stand: 5 of the 48 ingredients carry a named published reference. The rest follow the calibration below and are labelled on their own pages as not yet sourced. We would rather show you that gap than paper over it. Sourcing the remainder is ongoing editorial work, and if you have a reference we have missed, please tell us.
The calibration anchors
Ingredients without an individual published reference are kept consistent with four anchor figures that almost every reference agrees on, so an unsourced entry is still a considered figure rather than a guess:
- Butter: 1 cup = 227 g, which is also two US sticks and half a pound. The least ambiguous figure in the kitchen, because butter is sold by weight in marked sticks.
- Water: 1 cup = 240 g, since 1 ml of water weighs 1 g.
- All-purpose flour: 1 cup = 125 g.
- Granulated sugar: 1 cup = 200 g.
What this site does not claim
There is no test kitchen here and nobody on this project weighs ingredients professionally. Claiming otherwise would be the fastest way to make everything else on the page suspect. What we do is narrower and checkable: collect published references, record what each one actually says, explain which figure we follow and why, publish the disagreements rather than hiding them, and correct the data when a reader shows us we are wrong. Every correction is dated in the changelog.
The figures are careful kitchen approximations, not laboratory measurements. For anything sensitive, weigh it.
Frequently asked questions
Which cup does this site use?
The US legal cup of exactly 240 millilitres, the definition the US Food and Drug Administration fixed for nutrition labelling in 21 CFR 101.9(b)(5)(viii). It is also the figure most modern American recipe writing assumes. Every gram value on the site is grams per that cup unless a page says otherwise.
Why do published cup weights disagree with each other?
Because a cup weight is not a physical constant, it is a measurement of how a particular ingredient happens to sit in a cup. Spooning flour in and levelling it off gives a noticeably lighter cup than scooping straight from the bag and pressing down. Published references make different assumptions about that, which is why King Arthur Baking publishes 120 grams for a cup of all-purpose flour where this site prints 125.
Are the ounces on this site fluid ounces?
No. Every ounce figure on this site is an ounce of weight, 28.3495 grams. One US cup is always 8 fluid ounces of volume whatever is in it, but its weight in ounces depends entirely on the ingredient: a cup of honey is 8 fluid ounces and about 12 ounces by weight.
How accurate are these figures?
Treat them as accurate to within a few percent. They are careful kitchen approximations, not laboratory measurements, and the biggest source of error is not the table but how you fill the cup. For bread, pastry and anything with yeast or chocolate, weighing on a scale removes that error completely.
Method last reviewed . Compiled by the CupsToGrams editorial team at FusionStudios.